The contract will enable the conduct of research to evaluate the environmental determinants of cancer, focusing on studies for which China offers unique etiologic opportunities. Three studies this contract are as follows: a case-control study of cancers of the penis and cervix in Human province; a cohort and case-control study of lung cancer in Yunnan province among tin miners exposed to three recognized carcinogens (tobacco smoke, radon, and arsenic); and a cohort study of silica-exposed workers in central and South China. The studies will provide new information on viral and other risk factors for penis and cervical cancers, will assess dose-response and interactive relations between radon, arsenic, and smoking in cancer risk, and will provide the largest investigation yet of lung and other cancers among persons highly exposed to silica.